Intermolecular Coordination Research Articles

Thiacalix[4]arene–alkali metal assemblies: crystal structures and guest-binding capabilities of supramolecular architectures supported by metal coordination and cation–π interactions

To investigate alkali metal complexation with sulfur-linked calixarene analogues and their guest-binding properties for gaseous organic guest molecules, we elucidated a crystal structure of a cesium complex with p-H-thiacalix[4]arene ( 1·4H) ligands and guest-binding properties of the cesium complex ( 2) and the previously reported rubidium complex ( 3). In crystals of the complex 2, a ‘sandwich-like’ binuclear complex was formed by inter-molecular coordination of cesium cations to the thiacalixarene molecules and methanol molecules, mutually interacting by aromatic-H⋯S hydrogen bonding and alkali metal cation–π interactions between the alkali metal cation and thiacalixarene aromatic rings outside of the cavities. On the guest-binding behaviors both complexes 2 and 3 toward organic guest molecules, methanol, ethanol, and 1-propanol as polar molecules, the complex 2 has no methanol adsorption ability, but the complex 3 showed vapor adsorption properties for all guest molecules. In particular, both complexes exhibited a high adsorption capability toward ethanol molecule. As results of gaseous guest adsorption measurements for alcohol molecules, the guest-binding of these complexes are significantly different because the properties depend heavily on structural natures between complexes 2 and 3.

Inorganic Electrosynthesis: a Green Chemical Method for tin Complexes

SnIV complexes of the series of bulky amines have been reported by electrochemical oxidation (3 h) of a tin anode in a cell containing methanol solution of the corresponding bulky amine. All were full characterized by 1H and 13C-NMR, IR, and high resolution mass spectrometry. However, all were not enough soluble in organic solvent in order to record its 119Sn-NMR spectra, this unusual behavior was attributed to the polymeric association thought intermolecular coordination OSn.

High selectivity toward cyclohexanol in oxidation of cyclohexane using manganese aminophenylporphyrins as catalysts

This work reports that the cyclohexane oxidation by iodosylbenzene and iodobenzene diacetate yields cyclohexanol as the sole product if catalyzed by the simple Mn(III) aminophenylporphyrins 5,10,15,20-tetrakis(2-aminophenyl)porphyrinatomanganese(III) chloride (Mn(III)(T2APP)Cl) and 5,10,15,20-tetrakis(4-aminophenyl)porphyrinatomanganese(III) chloride (Mn(III)(T4APP)Cl). This high selectivity was unmatched by other simple phenyl-substituted Mn(III) meso-tetraphenylporphyin-based catalysts (Mn(III)(T- X-PP)Cl, where X = H, 4-OMe, 4-Me, 4-CO 2Me, 2-Me), which led to a mixture of both cyclohexanol and cyclohexanone. The absence of cyclohexanone in the Mn(III)(T2APP)Cl and Mn(III)(T4APP)Cl as well as the possibility of re-use of the catalysts was investigated. An intermolecular coordination of the amino moieties in Mn(III)(T2APP)Cl and Mn(III)(T4APP)Cl is suggested to play a role in the high selectivity of these systems.

Gas-phase study of new organozinc reagents by IRMPD-spectroscopy, computational modelling and tandem-MS

An extensive set of organozinc iodides, useful for Negishi-type cross-coupling reactions, are investigated as respective cations after formal loss of iodide in the gas phase. Firstly, two new alkylzinc compounds derived from Tyrosine (Tyr) and Tryptophan (Trp) are closely examined. Secondly, the influence of specific protecting groups on the subtle balance between intra- and intermolecular coordination of zinc in these reagents is probed through trifluoroacetyl (TFA)-derivatized alkylzinc compounds. Finally, the influence of the strongly coordinating bidentate ligand N,N,N',N'-tetramethylethylenediamine (TMEDA) on the structure of alkylzinc cations is further explored in order to better understand the stability of the respective complexes towards water. A combination of electrospray (ESI)-MS/MS, accurate ion mass measurements, infrared multiple-photon dissociation (IRMPD) spectroscopy and computational modelling allowed the full characterisation of all dimethylformamide (DMF)-solvated and TMEDA-coordinated alkylzinc cations in the gas phase. The calculations indicate that the zinc cation in gas-phase alkylzinc-DMF or TMEDA-complex ions preferentially adopts a tetrahedral coordination sphere with four ligands. Additionally, conformers with only three binding partners bound to zinc but with effectively combined hydrogen-bond interactions are also found. Collision induced dissociation (CID) patterns demonstrate that the zinc-DMF interaction in tetrahedral four-coordinate mono-DMF-zinc complex ions as well as the interaction between TMEDA and zinc in the corresponding complex ions is even stronger than typical covalent bonds. In most cases, all major features of the IRMPD spectra are consistent with only a single major isomer, allowing secured identification and assignment.

ChemInform Abstract: Recent Developments in the Chemistry of Stable Doubly Bonded Germanium Compounds

Abstract During the last 10 years, several compounds of the type Ge=X (X = C, Ge, N, P, S) have been isolated as monomers. The stabilization of such derivatives, which are generally highly polymerizable, was achieved by using very bulky groups both on the germanium atom and on the heteroelement X. Conjugation (particularly in a few germenes and germaimines) and intramolecular or intermolecular coordination with oxygen or nitrogen, also contributes, in some cases, to the stabilization. The X-ray analyses of such compounds show a significant bond shortening of the double bond (8–10%) relative to the corresponding single bond and a planar or nearly planar germanium. These doubly bonded germanium derivatives are usually thermally stable but must be handled in an inert atmosphere because of their high sensitivity to oxygen and moisture; they are extremely reactive, much more than the corresponding carbon analogues. Nearly quantitative additions on the double bond have been observed with electrophiles and nucleophiles, and various types of cycloadditions also occur. Except in one case, a germylene behavior has not been observed, proving that such compounds retain their structural integrity in solution.

A coordinated molecular ‘fishing’ mechanism in heterodimeric kinesin

Kar3 is a kinesin motor that facilitates chromosome segregation during cell division. Unlike many members of the kinesin superfamily, Kar3 forms a heterodimer with non-motor protein Vik1 or Cik1 in vivo. The heterodimers show ATP-driven minus-end directed motility along a microtubule (MT) lattice, and also serve as depolymerase at the MT ends. The molecular mechanisms behind this dual functionality remain mysterious. Here, a molecular mechanical model for the Kar3/Vik1 heterodimer based on structural, kinetic and motility data reveals a long-range chemomechanical transmission mechanism that resembles a familiar fishing tactic. By this molecular ‘fishing’, ATP-binding to Kar3 dissociates catalytically inactive Vik1 off MT to facilitate minus-end sliding of the dimer on the MT lattice. When the dimer binds the frayed ends of MT, the fishing channels ATP hydrolysis energy into MT deploymerization by a mechanochemical effect. The molecular fishing thus provides a unified mechanistic ground for Kar3's dual functionality. The fishing-promoted depolymerization differs from the depolymerase mechanisms found in homodimeric kinesins. The fishing also enables intermolecular coordination with a chemomechanical coupling feature different from the paradigmatic pattern of homodimeric motors. This study rationalizes some puzzling experimental observation, and suggests new experiments for further elucidation of the fishing mechanism.

Heteronuclear Double Bonds E=E′ (E = Heavy Group 14 Element, E′ = Group 13–16 Element)

Abstract A number of compounds with heteronuclear double bonds between heavy elements of groups 13, 14, 15, and 16 have been isolated and characterized in the last three decades; they are kinetically stabilized by the use of bulky substituents or thermodynamically stabilized by intra- or intermolecular coordination. They are fascinating compounds in respect of their unusual chemical properties, being very useful building blocks in organometallic chemistry.

β‐Diketiminate Zinc Complexes for the Hydroamination of Alkynes

AbstractA series of electronically and sterically modified β‐diketiminate methylzinc complexes [{N,N′‐bis(2,6‐diisopropylphenyl)‐β‐diketiminato}methylzinc] (1), [{N,N′‐bis(2‐isopropylphenyl)‐β‐diketiminato}methylzinc] (2), [{N,N′‐bis(2,4,6‐trimethylphenyl)‐β‐diketiminato}methylzinc] (3), [{N,N′‐bis(4‐methoxyphenyl)‐β‐diketiminato}methylzinc] (4), a bis(β‐diketiminato)zinc compound [bis{N,N′‐bis(4‐methoxyphenyl)‐β‐diketiminato}zinc] (5), and a β‐diketiminate bis(trimethylsilylamido)zinc complex [{2‐(1‐cyclohexylimidazolidine‐2‐ylidene)‐1‐methylethylidene‐(2,6‐diisopropylphenyl)aminato}bis(trimethysilylamido)zinc] (6) were prepared and structurally characterized by single‐crystal X‐ray diffraction. All methylzinc compounds exhibit a trigonal‐planar coordinated zinc atom, with the exception of polymeric compound 4, in which intermolecular coordination of the OMe group to the zinc atom additionally takes place. All zinc complexes were investigated as catalysts in the intramolecular hydroamination of nonactivated alkynes and show high catalytic activity in the presence of the cocatalyst [PhNMe2H][SO3CF3]. The zinc complex 1 shows the highest catalytic activityin most of the cyclization reactions. In this context, it waspossible to isolate the intermediate, which was formed bythe reaction of the precatalyst 1 and the cocatalyst [PhNMe2H][SO3CF3]. The resulting zinc catalyst [{N,N′‐bis(2,6‐diisopropylphenyl)‐β‐diketiminato}(trifluoromethanesulfonate)zinc]·thf (7) was structurally characterized by single‐crystal X‐ray diffraction. The zinc complex 7 show the same catalytic activity in the hydroamination when an equimolar mixture of the precatalyst 1 and the cocatalyst was used. It is supposed that the high steric bulk of the precatalyst 1 protects the Lewis acid zinc center from polar functional groups but allows interactions for the cyclization process.

Crystal structure of N-(3-hydroxypropyl)-β-alanine and Bis(N-(3-hydroxypropyl)-β-alaninato)dicopper(II) [Cu2 (Pro-ala)2

N-(3-Hydroxypropyl)-β-alanine was synthesized by the reacti on of 3-aminopropanol with acrylic acid. From this ligand and basic copper carbonate, bis(N-(3-hydroxypropyl)-β-alaninato)dicopper(II) [Cu2 (C6H11NO3)2] was obtained. The structures of the chelating agent and the copper complex were studied by X-ray diffraction. The Cu(II) coordination polyhedron is a distorted square pyramid. Each ligand forms six-membered β-alaninate and propanolamine chelate rings. The propoxy group functions as a bridge. In the crystal structure, the molecules form intermolecular coordination bonds C=O→Cu, which are perpendicular to the layers. The EPR signal typical of dimeric copper complexes is not observed due to low occupancy of the excited paramagnetic triplet state. The weak paramagnetic signal from monomeric copper complex allowed recording of the 1H NMR spectrum of [Cu2 (Pro-ala) 2] with characteristic line broadening and contact shift. It follows from the obtained data that on dissolution, the complex dissociates by 40% to give monomeric copper complexes.

Zinc(II), Copper(II), and Nickel(II) Complexes of Bis(tripodal) Diamide Ligands – Reversible Switching of the Amide Coordination Mode upon Deprotonation

AbstractA series of dinuclear Zn(II), Cu(II) and Ni(II) complexes of two new bis‐tripodal ligands with aromatic (H2‐4a) and aliphatic (H2‐4b) diamide spacers has been synthesized and structurally characterized. Each of the two tripodal entities of the neutral dinucleating ligands coordinates to one metal ion via three amine functions and a carbonyl oxygen atom of the amide groups. Either trifluoroacetate counterions or solvent molecules complete the trigonal‐bipyramidal (Zn, 5a), square‐pyramidal (Cu, 6a and 6b), and octahedral (Ni, 7a and 7b) coordination environment at the metal centers. Complexes 5a, 6a, and 7a with the phenylene‐bridged diamide ligand are readily deprotonated by potassium tert‐butoxide effecting a rearrangement of the dinuclear complexes. In the resulting zinc and copper complexes 8 and 9, one of the metal centers is coordinated by three amine functions of a tripodal subunit and the two amidate nitrogen atoms of the deprotonated ligand 4a2– while the coordination geometry of the second metal atom remains unchanged. The analogous nickel compound crystallizes as neutral tetranuclear complex (10)2 with intermolecular coordination of two amide carbonyl oxygen atoms to the nickel atoms of an adjacent dinuclear complex. The resulting coordination mode with binding of all four donor functions of the diamide spacer to three discrete metal centers is to date unprecedented for ortho‐phenylene‐bridged acetamides. The rearrangement upon deprotonation has been shown to be fully reversible and the starting complexes can be retrieved upon protonation of the two amidate functions. Synthesis of the trinuclear zinc complex 11 with coordination of the two amidate nitrogen atoms to a third metal center was achieved via deprotonation of (H6‐4a)(CF3CO2)4 by three equivalents of diethylzinc. In protic solvents 11 rapidly rearranges to give the entropically favored dinuclear complex 8 with elimination of one equivalent of zinc trifluoroacetate.

An energy dispersive x-ray scattering and molecular dynamics study of liquid dimethyl carbonate

In this work, we report on the first x-ray diffraction study on liquid dimethyl carbonate. Diffraction spectra were collected with an energy-dispersive instrument, whose wide Q-range allows the structure determination of weakly ordered systems (such as liquids). The structural correlation in this liquid ranges up to about 20 A. The observed patterns are interpreted with a structural model derived from classical molecular dynamics simulations. The simulations were run using OPLS force field, only slightly modified to restrain bond distances to the experimental values. The model structure function and radial distribution functions, averaged among the productive trajectory frames, are in very good agreement with the corresponding experimental ones. Molecular dynamics results show that the deviations from C(2v) cis-cis structure, predicted by ab initio calculations and observed by electron diffraction in the gas phase, are small. By analyzing the intra- and intermolecular pair distribution functions, it was possible to assign the peaks of the experimental radial distribution function to specific structural correlations, and to compute the different average intermolecular coordination numbers. The intermolecular methyl-carbonyl oxygen distance is thoroughly discussed to assess the presence of weak C-H...O hydrogen bonds.

Transmetallation and silylation products of aminal carbanions

Reactions of the lithiated carbanion [(RLi)(2).(RH)] (R = MeN[CH(2)N(Me)](2)CH, 2,4,6-trimethyl-2,4,6-triazacyclohex-1-yl) with dialkylaluminium and -gallium chlorides lead to the corresponding dialkylaluminium and -gallium compounds (RAlMe(2))(2), (RAlEt(2))(2) and (RGaEt(2))(2). They were characterised by elemental analyses, NMR spectroscopy ((1)H, (13)C, (27)Al) and crystal structure determinations. In the solid state the aluminium and gallium compounds form dimers by intermolecular coordination between the metal acceptor and the nitrogen donor leading to six-membered M(2)C(2)N(2) rings in chair conformation. As a first test for the synthetic utility of [(RLi)(2).(RH)], nucleophilic aminomethylation of chlorotrimethylsilane was performed to give RSiMe(3). Further deprotonation of RSiMe(3) with tBuLi occurs at one of the methyl groups bound to the silicon atom leading to RMe(2)SiCH(2)Li. Reactions with dimethylaluminium and -gallium chlorides gave RMe(2)SiCH(2)AlMe(2) and RMe(2)SiCH(2)GaMe(2). The compounds were characterised by NMR spectroscopy ((1)H, (13)C, (29)Si, (27)Al), elemental analyses and single crystal X-ray diffraction. The compounds are monomeric in the solid state with intramolecular M-N bonds (M = Al, Ga) leading to five-membered rings.

Electrical and Thermal Properties of Azo-Metal Complexes used as Charge-Control Agents

The authors have recently proposed a novel charge-control mechanism that assumes an appreciable temperature increase at the "toner/carrier" interface due to the triboelectrification. In this model, the temperature dependence of the electrical conductivity of charge-control agents (CCAs) plays the crucial role. Therefore, electrical and thermal properties of azo-metal complexes used as CCAs have been investigated in order to provide additional evidence for our model as well as to study their high thermal stability. The electrical conductivity of a typical azo-Fe complex (i.e., T-77 from Hodogaya Chemical) is found to increase exponentially with temperature, and the value around 100° C is about two to three orders of magnitude higher than that at room temperature. This supports our charge-control mechanism. On the other hand, the structure analyses of T-77, sodium salt of T-77, and sodium salt of a Cr-complex revealed that there are intermolecular hydrogen-bond networks or coordination networks, in which each cation bridges neighboring anions. This type of network is found to be responsible for high thermal stability above 250° C.

Versatility and dynamics of the copper(i) coordination sphere in sterically hindering tris(pyrazolyl)methane-incorporating macrobicycles

Two arene-capped macrobicycles (1 and 2) incorporating the tris(pyrazolyl)methane (Tpm) chelate have been prepared from a benzylthiol-functionalized Tpm precursor (3). Reaction of either macrobicycle with Cu(CH3CN)4+ leads to tetrahedral or trigonal-planar, fluxional complexes incorporating the Cu(CH3CN)+ subunit ([Cu(1)(CH3CN)]+ and [Cu(2)(CH3CN)]+). The acetonitrile ancillary ligand does not fit inside the macrobicycle cavity and can be removed by heating under vacuum, which produces the [Cu(1)]+ and [Cu(2)]+ species probably involving intramolecular thioether coordination. The [Cu(1)(CH3CN)]+ complex was shown to convert slowly in wet acetone into a helical coordination polymer, which is formulated as [Cu(1)(H2O)]nn+. In the crystal, the metal cation in tetrahedral geometry is bound to two pyrazole nitrogens and bridges two macrobicyclic subunits by intermolecular thioether sulfur coordination. Its coordination sphere is remarkably completed by a water molecule that is located inside the macrobicycle and is bound to the uncoordinated pyrazole fragment and to the mesitylene cap by OH⋯N and OH⋯π hydrogen bonding interactions.

Use of73Ge NMR Spectroscopy for the Study of Electronic Interactions

The lack of understanding of the structural and electronic factors that affect the often difficult to observe germanium resonance has been a major deterrent to studies of bonding interactions at germanium. We utilized the symmetrical system GeR 4 to determine what structural factors inherent in the R group affect the shape and position of the (73)Ge resonance. The (73)Ge resonances of symmetrical tetrakis germanium compounds of the type GeR 4 (R = alkyl, aryl), GeX 4 (X = F, Cl, Br, I), Ge(OR) 4 (R = alkyl, methoxyalkyl, dimethylaminoalkyl), Ge(NR 2) 4 (R = alkyl), and Ge(SR) 4 (R = alkyl, dimethylaminoalkyl) were examined for evidence of intramolecular coordination. Although many of these compounds have sharp resonances due to idealized tetrahedral symmetry with relatively long relaxation times, others have broad or no observable resonances due to fast quadrupolar relaxation. We hypothesize that the perturbation of symmetry by even weak Lewis interactions or conformational changes causes broadening of the resonance before the interaction can become sufficiently strong to cause the significant low-frequency shift generally associated with hypercoordination in most nuclei. Intermolecular coordination to GeCl 4 is believed to be responsible for the low-frequency shifts in (73)Ge resonances and the associated changes in peak widths in mixtures with bases such as tributylphosphine oxide (TBPO) and triethylphosphine oxide (TEPO). Adduct formation with these bases is confirmed by broad (31)P resonances that are resolved into five peaks at -40 degrees C. The exchange-broadened resonances due to the 1:1 and 1:2 TEPO adducts are also observed at -40 degrees C in the (73)Ge spectrum. Thus, relatively strong bonding to the germanium in GeCl 4 results in both low-frequency shifts and broadening of the resonance. The broad (73)Ge resonances that occur in some compounds may be in part due to exchange as well as quadrupolar relaxation.

Structural and Catalytic Aspects of Dioxomolybdenum(VI) Complexes with ω‐Hydroxy Functionalized N‐Salicylidene Hydrazides

AbstractThe new cis‐dioxomolybdenum(VI) complexes [MoO2(salhyhb)]2 (1), [MoO2(salhyhp)] (2), and [MoO2(salhyhh)(MeOH)] (3) with the hydrazone ligands H2salhyhb, Hsalhyhp, and H2salhyhh derived from salicylaldehyde and ω‐hydroxy carbonic acid hydrazides with different chain lengths, have been synthesized and spectroscopically characterized. The crystal structures of all three complexes reveal an octahedral environment for the molybdenum atoms with the same basic structural motif. In addition to the two oxo groups an [NO3] donor set is observed which is given by the tridentate Schiff‐base ligand and an oxygen atom of a coordinating alcohol. Depending on the side chain length different modes of association are observed. For complex 1 a dimeric structure is obtained, which is linked by coordination of the side chain hydroxy group at the molybdenum atom of the other monomer. The extension of the side chain by one methylene group in complex 2 leads to a polymeric structure, which is based on a similar intermolecular coordination of the side chain hydroxy group. The further increase of the side‐chain length in complex 3 results in the coordination of a methanol molecule at the molybdenum atom. For compounds 2 and 3 the additional hydrogen‐bonding network leads to the formation of layered structures in the solid state. The synthesized cis‐dioxomolybdenum(VI) complexes were tested for their catalytic ability towards the oxidation of sulfides. Although no significant influence of the side chain lengths could be detected, these complexes are efficient catalysts for sulfoxidation.

Synthesis and structural characterization of a new self-assembled disulfide linked meso-tetrakis-porphyrin macromolecular array

The synthesis of a new self-assembled porphyrin macrostructure based on disulfide bonds, is presented. This constitutes a new way to directly connect porphyrins in macromolecular arrays, to complement the usual methods of intermolecular hydrogen bonds and metal coordination bonding.

Effects of Hydration on Mechanical Properties of a Highly Sclerotized Tissue

The jaws of the bloodworm Glycera dibranchiata consist principally of protein and melanin scaffolds with small amounts of unmineralized copper (Cu) and mineralized atacamite (Cu2Cl(OH)3) fibers in distinct regions. Remarkably, when tested in air, the regions containing unmineralized Cu are the hardest, stiffest, and most abrasion resistant. To establish the functions of jaw constituents in physiologically relevant environments, this study examines the effects of hydration on their response to indentation, scratching, and wear. Although all jaw regions are degraded by the presence of water, the ones containing unmineralized Cu are affected least. Notably, scratch depths in the bulk and the atacamite-containing regions double when wet, whereas the corresponding increase in the regions with unmineralized Cu is ∼20%. The results support the view that Cu ions are involved in the formation of intermolecular coordination complexes, creating a cross-linked molecular network that is both mechanically robust and resistant to water ingress. Hydration effects are greatest during wear testing, rates of material removal in water being about three times those in air. The mechanism underlying accelerated wear is suspected to involve coupled effects of near-surface damage and enhanced water ingress, resulting in increased plasticization and susceptibility to plastic plowing.

Phase Behavior of Polystyrene-block-poly(4-vinylpyridine) Copolymers Coordinated by Metal Chloride

The effect of cadmium chloride (CdCl2) on the phase behavior of polystyrene-block-poly(4-vinylpyridine) copolymer (S4VP) was investigated by using rheometry, small-angle X-ray scattering, and transmission electron microscopy. For this purpose, symmetric S4VPs with various molecular weights were prepared by anionic polymerization. We found that with the addition of CdCl2 the order-to-disorder transition of S4VP was significantly increased because of the intermolecular coordination connecting different P4VP block chains. We also studied the change of the domain spacing (D) upon addition of CdCl2 as well as gelation behavior. At a relatively low content of CdCl2 (γ < 6, where γ is the number of coordinated CdCl2 per chain), D remains unchanged. However, when the amount of CdCl2 increases further, D begins to decrease due to many coordinations of CdCl2 that strongly perturb block copolymer conformation, including many ring closures. Furthermore, it is found that the scaled gelation point increases with increa...

Site-Specific Solvation of the Photoexcited Protochlorophyllide a in Methanol: Formation of the Hydrogen-Bonded Intermediate State Induced by Hydrogen-Bond Strengthening

The site-specific solvation of the photoexcited protochlorophyllide a (Pchlide a) in methanol solvent was investigated using the time-dependent density functional theory method for the first time to our knowledge. The intermolecular site-specific coordination and hydrogen-bonding interactions between Pchlide a and methanol molecules play a very important role in the steady-state and time-resolved spectra. All the calculated absorption and fluorescence spectra of the isolated Pchlide a and its coordinated and hydrogen-bonded complexes with methanol demonstrate that the novel fluorescence shoulder at ∼690 nm of Pchlide a in methanol should be ascribed to the coordinated and hydrogen-bonded Pchlide a-(MeOH) 4 complex. This coordinated and hydrogen-bonded complex can also account for the intermediate state found in the time-resolved spectroscopic studies. Herein, we have theoretically confirmed that the intermolecular coordination and hydrogen bonds between Pchlide a and methanol molecules can be strengthened in the electronically excited state of Pchlide a. Furthermore, the site-specific solvation of the photoexcited Pchlide a can be induced by the intermolecular coordination and hydrogen-bond strengthening upon photoexcitation. Then the hydrogen-bonded intermediate state is formed in 22–27 ps timescales after the site-specific solvation. All the steady-state and time-resolved spectral features of Pchlide a in different solvents can be explained by the formation of this hydrogen-bonded intermediate state after the site-specific solvation, which is induced by the coordination and hydrogen-bond strengthening.